1. Field of the Invention
The invention relates to a monitorable device for sealing off a body, in particular a garbage dump or a landfill, having two mutually spaced-apart seals defining a control chamber therebetween, the control chamber being closed except for connections for an inlet opening and an outlet opening for a transport medium, the inlet opening communicating with the outlet opening in the control chamber through a permeable channel or hose, and a sensor connected to the outlet opening for a substance to be monitored. The invention also relates to a method for monitoring such a device for sealing off a body.
2. Description of the Related Art
German Petty Patent No. G 91 07 693.5, generally corresponding to co-pending U.S. application Ser. No. 730,619, filed Jul. 16, 1991, discloses an element for sealing and monitoring a body, in particular a trash dump or landfill. The element includes two spaced-apart seals. A permeable channel or a hose for a transport medium, with an inlet opening on one end and an outlet opening on one end, is located between the seals. Except for leaving the openings free, the two seals are tightly joined together at edges thereof. A transport medium is fed into the inlet opening at predetermined time intervals. The outlet opening is connected to a sensor. If one of the two seals has a leak, then a substance, such as a pollutant, generally travels into the channel or hose from the outside. The substance is carried to the sensor along with the transport medium, and the sensor records the substance. If the flow speed of the transport medium is known, then a conclusion as to the site of the leak can be drawn from the instant when the substance enters the sensor.
In the case of locating leaks, a leakage locating system known from German Patent No. 24 31 907, corresponding to U.S. Pat. No. 3,977,233, for instance, is utilized.
With the known apparatus, a leak in one of the two seals can easily be detected if a substance which is a gas enters through the leak from the outside. It is then only necessary to use a suitable gas sensor. However, if the substance to be monitored is a liquid, in particular water or an aqueous solution, determining the leakage site becomes difficult. If the invading liquid is to be detectable in the transport medium, it is necessary for the transport medium to be primarily dry. If the transport medium were saturated with water, then water itself invading through a leak could not be recorded by a suitable water sensor. However, if the control chamber is primarily dry, the invasion of even a small amount of water represents a pronounced locally defined change in the water content in the control chamber. Such a water quantity can then be carried with the transport medium to the sensor. Since the transport medium is fed in at regular intervals, a conclusion as to the leakage site can be drawn from the instant of the entry of the water at the sensor.
It is technologically difficult to maintain a dry control chamber. Drying agents that even absorb moisture from the transport medium must be used in the control chamber. If the control chamber, for the sake of mechanical stability, contains a gas-permeable and liquid-permeable medium, then the medium must be kept dry as well.